The present disclosure relates to a headphone apparatus and a sound reproduction method for the headphone apparatus, and particularly to a headphone apparatus and the like which reproduces two-channel sound signals.
In the related art, there is a sound reproduction method according to which a headphone user (listener) wears a headphone on his/her head so as to cover both ears and listens to a sound signal (acoustic signal) from both ears. According to the sound reproduction method, a so-called lateralization phenomenon in which a reproduced sound image stays within the head of the listener even if a signal from the signal source is a stereo signal occurs.
On the other hand, there is a binaural collected sound reproduction method as a sound reproduction method by a headphone. The binaural collected sound reproduction scheme is a scheme as follows. That is, microphones called dummy-head microphones are provided for holes of both left and right ears of a dummy head on the assumption of the head of the headphone user. A sound signal from a signal source is collected by the dummy-head microphones.
If the headphone user actually wears the headphone and reproduces the thus collected sound signal, the headphone user can feel as if the headphone user were listening to the sound directly from the signal source. According to such a binaural collected sound reproduction method, it is possible to enhance a sense of direction, a sense of orientation, a sense of presence, and the like. However, it is necessary to prepare a signal source as a special source, which is different from a source for speaker reproduction, which collects sound source signals with a dummy-head microphone, in order to perform such a binaural collected sound reproduction method.
Thus, it can be considered that a reproduction effect that typical two-channel sound signals (stereo signals), for example, are used so as to be oriented outside a head (speaker positions) in the same manner as in speaker reproduction is obtained by applying the aforementioned binaural collected sound reproduction method by the headphone. In order to obtain sound image orientation outside a head with the use of a headphone, radiation impedance from entrances of external auditory canals of a headphone user to the outside becomes different from that in a case of a headphone non-wearing state.
That is, sound waves from the headphone repeats complicated reflection between ear auricles and headphone sound generating units and are transmitted from the entrances of external auditory canals to drum membranes. For this reason, even if it is attempted to transmit an optimal property to the entrances of external auditory canals or surfaces of the drum membranes, the reflection disturbs the property. Therefore, there is a disadvantage in that it is difficult to stably obtain a satisfactory sound image orientation.
For example, according to a headphone reproduction method described in Japanese Patent No. 3637596, a sound image orientation is enhanced by allowing radiation impedance from entrances of auditory canals to the outside to be close to that in the non-wearing state. That is, Japanese Patent No. 3637596 discloses that headphone sound generating units are positioned so as to be separate from ear auricles of a headphone user.